Once the Probe separated, what woke it up many months later just before entry?
The Probe had a built-in programmable timer, which was set by ground command shortly before the Probe separated from the orbiter. The Probe designers wanted to have some flexibility in starting the timer to accomodate any late changes in the Probe release schedule. If Probe release was delayed for any reason, the timer could be reset appropriately. The timer was the only thing running on the Probe during its five month long cruise to Jupiter. Like an alarm clock, the timer was set to wake up the Probe 6 hours before entry into Jupiter’s atmosphere so that the Probe could 1) take measurements of the inner magnetospheric energetic particle environment, and 2) listen for radio emissions characteristic of lightning (these actually sound like long, descending whistles). This “pre-entry” phase ended when the Probe’s accelerometers detected signs that the Probe was being decelerated by Jupiter’s atmosphere. At this point, the Probe started its entry/descent phase.
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- Once the Probe separated, what woke it up many months later just before entry?
